This invention relates to a wheel bearing assembly for supporting a vehicle wheel.
Among vehicle wheel bearing assemblies, there are ones for supporting driving wheels and ones for supporting non-driving wheels. Among both types of wheel bearing assemblies, there are many types.
FIG. 13 shows one example thereof. This wheel bearing assembly is for a driving wheel, and comprises an outer member 1, an inner member 11 and double-row rolling elements 31 mounted between the outer member 1 and the inner member 11.
On the inner periphery of the outer member 1, two raceways 3 are formed while on the outer periphery thereof, a flange 2 for mounting to the vehicle body is provided.
The inner member 11 has a hub ring 12 and a raceway member 13. A wheel-mounting flange 15 is provided on the outer periphery of the hub ring 12 at one end thereof. At the other end, a small-diameter portion 12b is formed on which is fitted the raceway member 13.
On the outer peripheries of the hub ring 12 and the raceway member 13, raceways 16 and 20 are formed, respectively. Between the raceways 16, 20 and the raceways 3 of the outer member 1, the rolling elements 31 are mounted.
In order to impart a pre-load to the rolling elements 31, a spline shaft 14c provided on an outer joint member 14 of a constant-velocity joint is mounted into a spline hole 17 formed in the hub ring 12, and a nut 21 is tightened on a threaded shaft 14d provided at the tip of the spline shaft 14c. 
The wheel bearing assembly is delivered from a wheel bearing manufacturer to an automobile assembling factory of an automotive manufacturer. At the factory, a separately delivered brake rotor 40 is fixed to one side 15a of the wheel-mounting flange 15 of the wheel bearing assembly by tightening bolts 42.
After assembling, if there is a considerable run-out of the braking surfaces 40a of the brake rotor 40, the frictional force will not be constant, so that vibrations and abnormal noise, so-called brake judder are produced during braking.
In order to suppress vibrations and abnormal noise produced due to run-out of the braking surfaces 40a of the brake rotor 40, heretofore, increasing the machining accuracy of parts has been sought. But such a solution is time-consuming and results in higher cost.
Also, since machining errors of parts accumulate in assembling them, even if the machining accuracy of individual parts is increased, it is difficult to suppress run-out of the braking surfaces 40a of the brake rotor 40.
Further, on the brake rotor-mounting surface 15a of the wheel-mounting flange 15 and the surface 40b of the brake rotor 40 that abuts the brake rotor-mounting surface 15a, as shown in an enlarged view of FIG. 14A, there exist undulations. Thus, a combination of such undulations will largely influence the run-out of the brake rotor 40. Heretofore, at an automobile assembling factory, when the wheel-mounting flange 15 of the wheel bearing assembly and the brake rotor 40, which are delivered as separate parts, are assembled, various adjustments including phase-adjustment at positions where run-out of the wheel-mounting flange 15 and run-out of the braking surfaces 40a of the brake rotor 40 are maximum and minimum have been carried out. Such a method is troublesome and poor in workability.
Also, when the brake rotor-mounting surface 15a of the wheel-mounting flange 15 and the surface 40b of the brake rotor 40 are brought into abutment with each other, due to the above said undulations, an air gap is formed therebetween. When the wheel-mounting flange 15 and the brake rotor 40 are pressed against each other in mounting the wheel, as shown by single-dot chain line in an enlarged view of FIG. 14B, the brake rotor 40 is liable to deform due to the air gap.
Such a deformation of the brake rotor 40 increases run out of the brake rotor 40, thus causing brake judder.
An object of this invention is to suppress deformation of the brake rotor, thereby preventing brake judder in a simple and inexpensive manner.
According to this invention, there is provided a wheel bearing assembly comprising an outer member having two raceways on its inner periphery, an inner member having raceways on its outer periphery so as to be opposite to the raceways on the outer member, and rolling elements mounted between the raceways. One of the outer member and the inner member is formed with a wheel-mounting flange, the wheel-mounting flange having an outer face serving as a brake rotor-mounting surface. A film is disposed between the brake rotor-mounting surface of the wheel-mounting flange and an abutment surface of a brake rotor that abuts the brake rotor-mounting surface (see an enlarged view shown in FIG. 4A). In FIGS. 4A and 4B, A indicates the film.
If a film is disposed between the brake rotor-mounting surface of the wheel-mounting flange and the abutment surface of the brake rotor, since it fills the air gaps which can be a factor in deformation of the brake rotor when a wheel is mounted, deformation of the brake rotor is suppressed.
While the film is formed of a material softer than steel, too soft of a material such as rubber is not preferable because it will impair the rigidity of the brake rotor and the wheel. The film may be formed by bonding or applying a sheet of an age-hardening resin or a coating of which the major component is an age-hardening resin to the brake rotor-mounting surface of the wheel-mounting flange or the abutment surface of the brake rotor that abuts the wheel-mounting flange.
The film that fills the air gaps, which can be a factor in deformation of the brake rotor, preferably has a thickness of 5 to 200 xcexcm.
The film may be provided on one or both of the brake rotor-mounting surface of the wheel-mounting flange and the abutment surface of the brake rotor that abuts the wheel-mounting flange.
By using an age-hardening resin sheet or a coating of which the major component is an age-hardening resin as the material for the film, the mounting rigidity of the brake rotor after mounting the wheel can be assured.
Also, by using a thermosetting resin as the material for the film and providing a simple heating step on the assembly line, the mounting rigidity of the brake rotor after mounting the wheel can be assured.
According to this invention, there is also provided a wheel bearing assembly comprising an outer member having two raceways on its inner periphery, an inner member having raceways on its outer periphery so as to be opposite to the raceways on the outer member, and rolling elements mounted between the raceways, one of the outer member and the inner member being formed with a wheel-mounting flange, the wheel-mounting flange having an outer face serving as a brake rotor-mounting surface, characterized in that a plurality of hub bolts are embedded in the wheel-mounting flange and that the contact force between the wheel-mounting flange and the brake rotor when a wheel is tightened to the hub bolts is concentrated at portions near the hub bolts.
As a means for concentrating the contact force between the wheel-mounting flange and the brake rotor at portions near the hub bolts, a chamfer at an edge of each of the holes for the hub bolts formed in the brake rotor may be set to 0.5 mm or under or recesses may be formed between the hub bolts in bolt pitch circle areas on one side of the wheel-mounting flange.
By concentrating the contact force between the wheel-mounting flange and the brake rotor when a wheel is tightened to the hub bolts at portions near the hub bolts, even if there are undulating components on the brake rotor-mounting surface of the wheel-mounting flange and the surface of the brake rotor that abuts the brake rotor-mounting surface, the undulating components will not become a factor in deformation of the brake rotor. Thus it is possible to suppress deformation of the brake rotor and also the run-out of the brake rotor.
Further, in order to suppress deformation of the brake rotor, the following means may be adopted.
When the hub bolts are pressed into the wheel-mounting flange, if swelling develops around the holes formed in the wheel-mounting flange, flatness of the brake rotor-mounting surface of the wheel-mounting flange worsens, thus constituting a factor in deformation of the brake rotor. Thus, the fitting interference between the hub bolts, which are formed with a knurled portion on their outer periphery, and the holes in the wheel-mounting flange into which the knurled portions of the hub bolts are pressed, is restricted to within a range of 0.1-0.4 mm to suppress swelling around the holes in the wheel-mounting flange, thereby improving flatness of the brake rotor-mounting surface of the wheel-mounting flange. Further, by forming the portions around the holes of the wheel-mounting flange into which the knurled portions of the hub bolts are pressed, in an unhardened state, it is possible to further suppress swelling around the holes in the wheel-mounting flange.
Further, by inclining the wheel-mounting flange toward the outer side at an angle of 20 minutes or under, the effect of suppressing deformation of the brake rotor can be further increased. Here, the outer side refers to the outer side in the width direction of the vehicle body.
By inclining it as above, when the brake rotor is brought into abutment with the brake rotor-mounting surface of the wheel-mounting flange and the disc wheel of the wheel is superposed on the brake rotor and the wheel nuts are tightened on the hub bolts to clamp the brake rotor and the disc wheel, the wheel-mounting flange is resiliently deformed, so that the outer peripheral portion of the brake rotor-mounting surface strongly abuts the brake rotor. Thus, the brake rotor is supported stably at the outer peripheral portion of its abutment surface relative to the brake rotor-mounting surface, so that it is possible to suppress run-out of the braking surface of the brake rotor during rotation.
If the inclination angle of the wheel-mounting flange is larger than necessary, the amount of resilient deformation of the wheel-mounting flange will be too small to bring the inner peripheral portion of the brake rotor into contact with the brake rotor-mounting surface of the wheel mounting flange when the brake rotor and the disc wheel are clamped by tightening the wheel nuts with a specified torque. In this case, mounting of the brake rotor will not be stable enough to suppress run-out of the braking surfaces of the brake rotor. Thus, the inclination angle of the wheel-mounting flange is preferably 20 minutes or less.
Also, if the run-out of the brake rotor-mounting surface of the wheel-mounting flange exceeds 30 xcexcm, run-out of the brake rotor during rotation would be so much that brake judder may develop. Thus, the run-out of the brake rotor-mounting surface of the wheel-mounting flange is preferably 30 xcexcm or under.
If the flatness at the outer peripheral portion and the circumferential flatness of the brake rotor-mounting surface of the wheel-mounting flange are 30 xcexcm or under, it is possible to suppress the run-out of the braking surfaces of the brake rotor to a small value.
The circumferential flatness refers to a dimension described below. With a measuring device B such as a dial gauge brought into contact with the outer peripheral portion of the brake rotor-mounting surface 15a of the wheel-mounting flange 15 as shown in FIG. 12A, undulating components in a circumferential direction are measured while rotating the wheel-mounting flange and they are developed on a plane and sandwiched by two parallel straight lines as shown in FIG. 12B. The circumferential flatness refers to the minimum distance xcex4 therebetween.
The wheel bearing assembly according to this invention may be one for a driving wheel or a non-driving wheel. Also, the wheel bearing assembly may be one in which a brake rotor is mounted to the wheel-mounting flange. If the run-out of the braking surfaces of the brake rotor is 50 xcexcm or less, favorable results are obtained in suppressing brake judder.